US1373624A

US1373624A - Automatic telephone system

Info

Publication number: US1373624A
Application number: US96495A
Authority: US
Inventors: Talbot G Martin
Original assignee: Automatic Electric Co
Current assignee: Automatic Electric Co
Priority date: 1916-05-10
Filing date: 1916-05-10
Publication date: 1921-04-05
Anticipated expiration: 1938-04-05

Description

T. G. MARTIN.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED MAY 10. 1916.

Patented Apr. 5, 1921.

2 SHEETSSHEET 1.

I. G. MARTIN.

AUTOMATiC TELEPHONE SYSTEM.

APPLICATION FILED MAY 10, 1915.

13735624. Patented Apr. 5, 1921.

2 SHEETS-SHEET 2.

WV MQW UNITED 3T TEES Parent OFFPECE.

TALBOT Gr. MARTIN, OF CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Specification of Letters Patent. Patented Apr. 5, 1921,

Application filed May 10, 1916. Serial No. 96,495.

To all whom it may concern Be it known that. I, TALBOT G. MARTIN, a citizen of the United States of America, and a resident of Chicago, Cook county, Illinois, have invented certain new and useful Improvements in Automatic Telephone Systerns, of which the following is a specification.

This invention relates to improvements in automatic telephone systems and more particularly to improvements in theautomatic switches used in such systems.

In many automatic telephone systems where ringing current is automatically applied to signal the called line when connection is established therewith, an interrupt 111g device is employed to control the application of ringing current at certain intervals. Usually this interrupting device is common-to a group of lines or common to all the lines in the exchange, depending on the size of the exchange and the particular arrangement desired. It a connection is completed to a called line just after the ringing interval, the called line will not be signaled until the interrupting device reaches its next ringing interval. The pe riod between ringing intervals is of some duration and it is therefore readily seen that some loss of time must be experienced before the substation signal of the called' line is operated.

It is an ObJGCiJ oi this 1nvent1on to provide means whereby ringing current for signaling purposes is projected to the called line the instant connection is completed therewith.

A further object of this invention is the provision of an arrangement of this char acter whereby afterthe initial signaling operation, the interrupting device controls the further ringing operation in the regular manner. 1 7

It is frequently impossible to limit the length of telephone lines leading from the subscribers stations to the exchange, especially is this true in outlying exchanges wherelines extending from farm substations are served. Even in city exchanges some lines are of greater length and therefore greater resistance than others. In these instances provisions must be made for the eflicient control oi": certain relays in the exchange by the longer lines which are necessarily of higher resistance than the shorter lines. In the switching mechanism herein disclosed ringing current for signallng purposes is supplied through a relay which is so constructed and adjusted that it will not operatively energize during the signaling operations. In order that the said relay may. properly operate to cut oil the ringing when in circuit with a line of high resistance, I provide means comprising a booster battery'of such voltage as will permit suflicient flow of current to insure positive operation.

To the foregoing and other useful ends my invention consists of matters hereinafter set forth in the description of the drawings and in the appended claims.

The features of this invention will be more clearly understood by reference to the accompanying drawings in which Figures 1 and 2 taken together represent a complete connection in an automatic telephone system embodying the principles of this invention.

The substation A (Fig, 1) comprises the usual receiver 3, transmitter 4E, ringer 5, condenser 6, switch hook 7. It is also provided with a suitable impulse-sending mechanism or calling device for controlling automatic switches, which mechanism is represented by a pair of impulse springs 8 and an impulse wheel 9, which latter may be controlled by a finger hold dial (not shown) in such a way that the impulse springs are momentarily separated a number of times corresponding to the respective digits of the called number. This impulse-sending mechanism may 'be similar to that shown in United States Letters Patent to J. G. Blessing, No. 1,119,394, granted December 1-, 1914;.

T he subscribers individual or line switch (I is of the general type of line switch disclosed in British patent to T. G. Martin No. 1419 or 1910, being however, of the particular type disclosed, in United States Letters Patent to F. Newforth, Jr., No. 13,901, reissued April 13, 1915. The line switch comprises among other details the magnet 10 and slow acting line relay 11. Themagnet 10 controls the cutoff arm 12 and plungerarm 13 through the medium of the pull-in winding 14 and cut-on winding 15. The winding 14: is strong enough to attract both the cut-off arm 12 and the plunger-arm 13 while the winding 1.5 is only strong enough to attract the cut-off arm 12 but will hold the plunger-arm 18 in its attracted position after it has been operated by the winding .14. The plunger-arm 13 carries on its end a plunger (not shown) which when operated forces the master switch D.

The master switch D is o1 the general type disclosed in British patent to lit. W. James No. 26,301 of 1906, being however, of the particular type disclosed in the previously mentioned British patent to T. li/lartin. As herein represented the master switch comprises the starting relay 2 locking magnet 25, motor magnet 26, and master switch wiper 27. The function of the master switch, as is well known, is to maintain the plungers of all idle line switches in position to engage the terminals of an idle trunk line.

The selector switch E is of the general type-oi": selector switch disclosed in United States Letters Patent No. 815,321, granted March 13, 1906, to Keith, Erickson and Erickson, except that the'side switch is dis pensed with and the circuits are modified to adapt the switch to o erate in a system in which the central otlice apparatus is 0011- trolled by impulses delivered over the two sides of the line in series. This selector being of the particular type disclosed in British Patent No. 254:3 of 1914 to Automatic Telephone Manufacturing (10., Ltd. Among other-details the selector comprises a bank of contacts arranged in horizontal rows or levels, which are adapted to be engaged by a set of wipers 28, 29, and 30, carried upon a shaft (not shown) which has a vertical and rotary movement controlled by the vertical and rotary magnets 31 and 32. The different operations of the sw1tch are controlled through the medium of the double- I wound line relay 3?). The release relay 84: and control relay 35 are slow-acting v1. 6., slow to release their. armatures when their energizing circuits are broken. The relay 86 controls the circuit of switching relay 37. The function of the latter being to eX- tend the connection through to the switch wipers. Therelease magnet 38 restores the switch shaft and wipers to normal position whereupon oil-normal springs 39 and 4.0 are separated. The said springs 39 and 40 are closed when the shaft takes one or more steps from its normal position.

The connector switch H 2) is of the general type of connector switch disclosed inUnited States Letters Patent No. 815,17 6

granted March 18, 1906, to Keith, Erickson V shown in British patent to T. G. Martin J No. 1 119 of 1910, and further modified to operate in accordance with the principles of my invention. Among other details the connector comprises a bank of contacts ranged in horizontal rows or levels which are adapted to be engaged by the wipers ll, 42, and 13 carried upon a shalt (not shown) which has a vertical and rotary movement controlled by the vertical and rotary magnets let and 45. The various operations of the switch are controlled through the medium of the line relay 46. The release relay 17, private control relay 18 and control relay 49 are slow acting, 2'. 6., slow to release their armatures when their energizing circuits are broken. The double wound relay 50 is made slow acting so that will not opcratively energize by ringing current when in the circuit of a condenser. The wiper cut-on relay 51 energizes when the side switch reaches its third position contacts. The privatemagnet 52 controls the advance of the wipers 53 and 5a in the well known manner. The busy relay 55 comprises two windings, the upper winding when energized attracts and operates its armature, while the lower winding will not operate the armature and is only used for resistance purposes as will be hereinafter esplained. The back bridge relay 56 supplies the called line with current for talking purposes. When energized the said relay 56 reverses the direction of current flow on the calling line which has no par ticular function in the present disclosure but may beused for any desired purpose. The release magnet 57 is the medium through which the switch is restored to its normal position. When the switch shaft reaches its normal position the off-normal springs 58 and 59 are separated.

These springs are closed when the shaft takes one or more steps from its normal position.

The group relay 60 is energized intermittently through the medium of the constantly rotating interrupter 61. When on crgized, said relay 60 supplies ringing current over a common circuit controlled by the springs 12a and 125 to a group of connectors, such as H, from the ringing current generator B. When deenergized said relay 60 disconnects the generator R and substitutes the booster battery B.

The battery B having its positive pole grounded is used to supply current for operating the automatic switches and for talking purposesa The battery B has its nega tive pole grounded and is connected in a series circuit with battery 13 when" relay 60 is deenergizedduring the signaling operation.

The busy signaling machine 1 comprising the transformer windings 62 and 63 and interrupter 64, is for the purpose of supplying a busy tone to the calling line when a connection is attempted witha busy line,

The line switch F is similar in all respects to the line switch C and comprises the cut-off winding 65, pull-in winding 66 and line relay 67. The substation J is similar in all respectsto the substation A.

A general description of the apparatus herein disclosed having been given it will now be explained how a connection can be established between the line of calling substation A and the line of called substation J. Since the apparatus herein disclosed is in general well known in the art and is described in the publications herein referred to, its operation will be explained in a more or less general manner.

When the subscriber at substation A removes his receiver preparatory to making a call, an energizing circuit 1s closed for the line relay 11 of the switch C. This circuit extends from ground G through springs 68, line conductor 69, transmitter 4, receiver 3, impulse springs 8, switch hook springs 70, return line conductor 71, springs 72, line relay 11, to the battery B. The line relay 11, upon energizing, closes the circuit for the pull-in winding 14 extendingirom ground G through springs 73, the said winding 1 1, and master switch controlling contact 74 to the battery 13. The winding 14: operates to thrust the plunger (not shown) on the end of the plunger-arm 13 into the bank of contacts 16-23 thereby forcing springs 16, 17, 18 and 19 into engagement with springs 20, 21, 22 and 23, respectively, thereby extending the connection to the selector switch E. The cut-oil arm 12 is operated to remove the line relay 11 from across the line. The relay 11 being slow acting, maintains the circuit of winding 14 for a short time after its own circuit is broken. When the connec tion is thus extended an energizing circuit is established for the line relay of the selector E. This circuit extends from ground G through the lower winding of said relay 33, springs 75, bank springs 23 and 19 over the circuit previously traced through substation A back over bank springs 16 and 20, springs 7 6 and the upper winding of said line relay 33 to the battery 13. Upon energizing, the said relay 33 closes a circuit from ground G through springs 77 and 78 and release relay Bi to the battery B. The relay 3 1, upon energizing, closes a circuit from ground G through springs 7 9, conductor 80, springs 21 and 17 to a point 81 where the cir'cuit'divides, one path extending through the holding winding 15 to the battery B, the other path extending over private normal conductor 82 to private bank contact 83 and multiples thereof. This ground potential protects the substation A against seizure as long as the receiver is removed from the switchhook. Due to the slow action of line relay 11 the circuit of winding 14 is maintained closed until after the holding ground from G is supplied over the conductor 30 to the winding 15 to maintain the plunger in its operated position.

Assuming the number of substation J to be 220, the calling subscriber now operates his calling device for the first digit 2, thereby causing the impulse springs 8 to be momentarily separated twice, each time breaking the circuit of the line relay 33. The slow acting relay 3% does not deenergize during the momentary interruptions of its circuit by the relay 33 and therefore each time the latter relay deenergizes an impulse is transmitted from ground G springs 77 and 8 1, springs 85, springs 36 and 87, relay 35, and the vertical magnet 31 to the battery 13. The vertical magnet receives two impulses over this circuit and operates to advance the switch shaft and wipers two steps to a position opposite the second level of bank contacts, at the same time the pairs of springs 39 and 10 are closed. The slow acting relay 35 ener izes when the first impulse of current is transmitted through it and holds its .armature attracted during the subsequent impulses of the digit. in its energized position said relay 35 closes a circuitfrom ground G through springs 83 and 39, and the relay 36 to the battery B. The relay 36, upon energizing, forms a locking circuit for itself from ground G springs 79, con ductor 80, springs 90, springs 40, springs 91 and 92, and the saidrelay 36, to the battery B. l/Vhen therefore, the relay 35 de energizes after the last impulse is delivered through it to the vertical magnet, the re lay 36 remains energized, and the circuit of the rotary magnet 32 is closed over a circuit that extends from ground G to springs 91 and 92 as previously traced, thence through springs 89 and 93, springs 9 1, and the rotary magnet 32 to the battery 13. The magnet 32, upon energizing, rotates the wipers 28, 29 and 30 one step and by opening the springs 90 and 9 1-, disconnects ground G from itseli and from the relay 36. 1f the first trunlrline of the second levelis idle the relay 33de'e'nergizes as soon as the springs 90 are opened. If this trunk line is busy however, the private wiper 29 finds the contact with which it engages provided with a guarding ground potential, which is transmitted to said relay 36 through its springs 91and 92 and tiereby prevents it from deenergizing. The rotary magnet 32 deenergizes when springs 94 are separated regardless of whether or not the relay 36 remains energized. 11" the relay 36 remains energized the circuit of the rotary magnet will again be closed as soon as its armature falls back far enough to close springs 90 and 94. The rotary magnet will therefore energize again and rotate the wipers onto the second set of bank contacts which form the terminals of a second trunk line. If this second set is also busy the rotary magnet will be again energized in the above manner to continue the rotation until the private wiper 29 encounters the non-grounded contact of an idle trunk line, whereupon relay 36 deenergizes. The relay 36, upon deenergizing, breaks the rotary magnet circuit so that further rotation is impossible and closes the circuit of switching relay 37 which extend from ground G through springs 79, conductor 80, springs 90, springs 40, springs 91 and 95 and the switching relay 37 to the battery B. The relay 37, upon energizing, disconnects the'line relay 33 from the line and extends the line connection over the heavy conductors through the wipers 28 and 30 to the connector H. The line relay 46 of said connector thereupon becomes energized and closes the circuit of release relay 47 from ground G7 through springs 96 and 97 and the said relay 47 to the battery B. The relay 47, upon energizing, completes a circuit from ground G through springs 98 and 99, release conductor 100, wiper 29, conductor 101 to a point 102, where the circuit divides, one path extending through springs 91 and 95 and the switching relay 37 to the battery B, the other path extending through springs 40, springs 90, springs 21 and 17 and the cut-off winding 15 to the battery B. A branch of the circuit taps off at point 81 and extends over conductor 82 to private contact 83 and its multiples. The above traced circuit maintains the relay 37 and holding winding 15 energized after the relay 34 deenergizes shortly after the line relay 33 is removed from the line.

The calling subscriber now operates the calling device for the second digit 2, whereupon the impulse, springs 8 are separated twice momentarily, each time breaking the circuit of line relay 46. y The relay 47 being slow acting does not deenergize during the momentary interruptions of its circuit by the relay 46, and therefore each time the latter relay deenergizes an impulse is transmitted over a circuit from ground G through springs 96and 103, springs 104, springs 105 and 1.06 of relay 51, relay 48, vertical magnet 44, and the side switch wiper 53 (in first position) to the battery B. The vertical magnet receives two impulses over this circuit and operates to advance the switch shaft carrying wipers 41,42 and 43 two steps to a position opposite the second row or level of bank contacts, at the same time springs 58 and 59 are closed. A circuit is then closed from ground G through springs 59, relay 49, springs 109 and 110 of relay 51 and the lower winding of relay 55 to the battery B. As before stated current flowing in the lower winding of55 will not attract its armature. Relay 49 energizes over this circuit and closes the contact of its springs 111 and 112. The relay 48 is energized by the first impulse which is transmitted through it to the vertical magnet and retains its armature attracted during the subsequent impulses of i the digit. In its energized position said relay 48 closes a circuit from ground G through springs 107 and 108 and the private magnet 52 to the battery B. This circuit is broken when the relay 48 deenergizes a short time after the last impulse has been delivered to the vertical magnet. The breaking of the circuit causes the privatemagnet to deenergize thuspermitting the side switch to pass from first to second position. In passing to second position the side switch wiper 53 transfers the battery connection to the rotary magnet 45. It should be noted that. one pole of the generator R is at this time connected through springs 112 and 111 (relay 49 being energized) springs 113 and 114 to spring 115 (relay 51 being as yet deenergized).

The callingfsubscriber now operates the calling device for the last digit 0, in response to which the connector line relay 46 operates to transmit ten impulses to the rotary magnet 45, whereby the shaft wipers are rotated onto the contacts of the de- 105 and 106 of relay 51, relay 48, springs 116 of relay 55, rotary magnet 45, side switch wiper 53 (in second position) to the battery B; The relay 48 operates in response to this digit in the same manner as for the previous digit to advance the side switch another step, 2'. a, from second to third position. Upon the engagement of the side switch wipers 53 and 54 with their third position contacts, a circuit is closed from ground G through wiper 54, relay 51, and wiper 53, to the battery B. A circuit is also closed from ground G through wiper 54, wiper 42, and the cut-off winding 65 of line switch F to the battery B. The wind ing operates to disconnect the line relay 67 of the called line. The relay 51, upon energizing, breaks the circuit of relay 49, but the latter being slow acting will retain its armature attracted for a short time atterits 'circuit is broken. A further result of the energization of relay 51 is the completion of the line circuit rover heavy conductorsthrough wipers 41 and '43 to the line of substation J. It should be noted that ringing ground. G through current will be immediately applied to the called line over a circuit that extends from the non-grounded terminal of the generatorR through springs 112 and 111 of relay 19, springs 113 and 11st of relay 50, springs 115 and 117, wiper 41, line conductor 11S, condenser and ringer of station J, return con ductor 119, wiper 13, springs 120, springs 121 and 122, left hand whirling of relay 550, battery B to ground and thence to generator ground G to other terminal of the generator When wiper 53 passes to third position another circuit is closed from ground G through interrupter 61., group relay 60, and side switch wiper to the battery B. The relay 60 is energized intermittently due to the insulated and noninsulated portions on the interrupter 61. The preliminary application of ringing current is controlled by the clay 4:9 and is therefore absolutely independent of the energizetion or deenergization of relay 60. springs 109 and 110 are separated due to the energization of relay 51 the circuit of relay 19 is broken; a short time after this occurs the latter relay deenergizes and closes its springs 111 and 123, thereby completing the generator circuit controlled by the interrupter relay 60 so that said relay 60 will thereafter intermittently connect the gencrater R to the called line. When relay 60 is energized and after relay 4:9 is deenergized ringing current flows from the non-grounded terminal of generator It through springs 12 1 and'125, springs 123and 111 thence over the circuit as previously traced over the called line. When relay G9 is deenergized, the booster battery B is connected over the same circuit through springs 126 and 125. The booster battery B will then be connected in a series circuit with the left-hand winding of relay 50 and the battery B. The function of the battery B, as before explained, is to provide an increased flow of current whereby telephone lines of high resistance will have no diiiiculty in operating relay 50 to cut oil the ringing. The relay 50 will not operatively energize when generator current flows through it in series with a condenser; however, as soon a direct metallic circuit is established the said relay 50 will attract and fully operate its armature. Upon the removal of the receiver at station J, current will. flow either from generator R or booster battery B depending upon position of spring 125, through springs 123 and 111, springs 113 and 114s, springs 115.and 117, wiper 41, line conductor 118, switch hook springs 127. impulse springs 128, receiver 129, transmitter 130, return line conductor 119, wiper 43, springs 1.29 springs 121 and 122, left hand winding of relay 59 to the battery B and ground either at ground G or grounded terminal of battery B. The relay 50, upon energizing, forms a locking When circuit from ground G through springs 59, springs 131 and the right hand winding of said relay 50 to the battery B. A further result of the euergization of relay 50 is the separation oif springs 11% and 113 and springs 121 and 122 and the closure of springs 11 and 132, as well as springs 121 and 133, whereby a circuit for the back bridge relay 56 is completed from ground G through springs 59, springs 131 of relay 59, right-hand winding of said relay 56, springs 13% and 121 to and through substation J as before traced to springs 114: and 132, thence through the leitdiand winding of relay 56 to the battery B. The backbridge relay 56 is the medium through which i the called subscriber is supplied with current for talking purposes. The said rela 56 upon energizing, reverses the direction 0 current flow on the calling line and by shitting spring 13a out of engagement with spring 185 and into engagement with spring 136 opens a contact in the circuit of release a magnet 57 and prepares a circuit for relay 4:8 The connections are new in talking condition and the subscribers may converse; talking current traveling over the heavy conductors.

Upon the completion of the conversation the connection will be released as follows, assumin that the called subscriber hangs up his receiver iirst and thereby deenergizes back-bridge relay 56. l Vhen the calling subscriber hangs up his receiver and thereby breaks the contact of springs 70, the circuit of line relay d6 of connector H is broken, which, upon deenergizing, breaks the circuit of relay e7, which in turn, upon debnergizing, removes the holding ground G from the release conductor 100, and in addition closes a circuit from ground G through springs 98 and 13'}, springs '58, springs 13 i and 135 and the release magnet 57 t0 the battery B. The release magnet, upon ener rizing, operates to restore the switch. sh aft side switch wipers to their normal position... its own circuit being opened when said shaft reaches its normal position and separates springs 58 and 59.

[is soon as private wiper -12 disengages bank contact 138, caused by the release of the connector, the circuit of winding 65 of-the switch F is broken to permit the line relay 6'? to be placed within control of the substation J. "When the holding ground is removed from the release conductor 100, the circuit of relay 37 and holding winding is broken, The relay 37, upon dee'ner- ;izing, closes a circuit from ground Gr hrough springs C 7 and 8%, springs 85, prings 86 and 139, springs 39 and the remagnet 38 to the battery B. The :se magnet, upon energizing, restores the switch shaft and wipers to normal position. The shaft upon reaching its normal position opens the circuit of said release magnet at springs 39. The deenergizatlon of winding 15 of the line switch C releases the plunger arm 13 and cut-off arm 12, thus permitting the withdrawal of the plunger from its bank contacts and the restoration of the line relay 11 across the conductors of the calling line. If, however, the calling subscriber restores his receiver to its switchhook before the called subscriber has done so, then the connector switch will not be released, but the selector E and line switch C will be returned to their normal position. This condition is brought about as follows: The calling subscriber upon hanging up his receiver, opens the circuit of the line relay 46 which opens the circuit of relay 47, the latter removing ground (i from'the con ductor 100v thereby permitting switches E and C to be releasedin the manner hereinbefore described. Relay 56 being now energized, a circuit will be closed from ground i through springs 98 and 137, springs 58, springs 134 and 136, springs 140 and 106, private control relay 48, conductor 141,

springs 142 and 110 of relay 51 and the lower winding of relay 55 to the battery B.

Relay 55 does not operatively energize at this time, its lower winding being for the purpose of reducing the current flow through relay 48. Relay 48 energizes over this circuit and closes a circuit from ground G through springs 107 and 108 and the private magnet 52 to the battery B. The private magnet upon energizing, closes a circuit from ground G through springs 143 over release conductor 100 to selector private bank contact 144 and multiples thereof. This ground potential protects the connector from seizure as longas it is held in this position. When the called subscriber hangs up his receiver thereby separating switch hook springs 127, the circuit of back bridge relay 56 is broken, thereupon deenergizing said relay to release the switch in the manner previously described.

If the called substation is busy there will be a guarding ground potential on private bank contact 138 and its multiples, there-- fore when connection isattempted and the private wiper 42 engages said contact, a circuit is closed from ground thereon over said wiper 42, side switch wiper 54 (in second position) through springs 145 and 146,

upper winding of relay 55, spring 147 and 108' and the private magnet 52 to the battery B. The relay 55 energizes over this circuit, to open the rotary magnet circuit at springs 116, to form a locking circuit for itself by forcing spring 148 into contact with spring 146 and separating spring 145 therefrom. This circuit extends from ground G through springs 59, springs 148 and 146, thence over the circuit previously traced. The relay 55 is held energized over this circuit and through the contact of its springs 149 supplies a busy tone from the busy machine I to the calling substation. The circuit for said tone extends from the battery lead through transformer winding 63, springs 149, over heavy conductors to and through substation A, back overheavy conductors and the upper winding of the line relay 46 to the battery lead. The sub scriber receives the tone in his receiver and upon recognizing the fact that the line is busy, restores his receiver to'release the automatic switches in a similar manner to that herein described;

t is thus seen that this invention contemplates a very efficient form of connector switch which applies ringing current to signal the called station as soon as connection is completed therewith. in this mannor the signal of the called station is in stantly operated. It is also seen that called lines are assisted in cutting off the ringing through the medium of the booster battery.

lVhile the illustration and description of this invention has been confined to an automatic switch of a particular type it is to be understood that I do not wish to be so limited as the principles herein set forth may be applied to various other circuit arrangements or types of apparatus without departing from the spirit and scope of this invention.

What I claim as my invention is:

1. In a. telephone system, a calling line, a called line, a plurality of progressively movable switches, any one, of which will serve the purpose of the calling line for establishing a connection to said called line, a signal for the called line, a source of current for operating said signal, a circuit in dividual to one of said switches, a circuit common to said switches, means for con necting said source over said individual circuit to operates-aid signal and for then connecting said source over said common circuit to said signal to operate the same, and means for interrupting said common circuit to intermittently operate. said signal.

2.1n a telephone system, a callinglin'e, a called line, a plurality of sets of progressively movable switches, any set of which will serve the purpose of the calling line for extending a connection to the called line, a signal for the called line, asource of current for operating said signal, acircuit common to said switches for connecting the said source with said signal when said connection is established, means for interrupting said circuit to intermittently operate said signal, and means including a circuit individual to one of said switches and independent of said interrupting means for connecting said source with said signal to operate the same. 7

3. In a telephone system, a calling line,

a called line, a plurality of progressively movable switches, means whereby the calling line finds one of said switches to extend a connection to said called line, a signal for said called line, a source of current for operating said signal, a circuit individual to one of said switches, a circuit common to said plurality of switches, means for connecting said source and said signal over said individual circuit to operate said signal and for then connecting saie source and said signal over said common circuit to operate said signal over said common circuit.

4. In a telephone system, a calling line, a called line, a plurality of progressively movable switches, means whereby the calling line finds one of said switchesto extend a connection to said called line, a signal for said called line, a source of current for operating said signal, a circuit individual to one of said switches, a circuit common to said plurality of switches, means for connecting said source and said signal over said individual circuit to operate said signal and for then connecting said source and said signal over said common circuit to operate said signal over said common circuit, and means for intermittently interrupting said common circuit to intermittently operate said signal.

5. In a telephone system, a line, a signal for said line, means for operating said signal, a plurality of circuits for connecting said means and said signal, means for shitting the line from one of said circuits to another to operate said signal over either of said circuits, vmeans for interrupting one of said circuits to intermittently operate said signal, a battery for operating said second means, another battery, said last means also for including said batteries in series with said line to enable said line to disconnect said first means.

6. In a telephone system, a line, a signal for said line, means for operating said signal, a pair of circuits for connecting said means and said signal, means for controlling the operation of said signal first over one of said circuits and then the other, means for interrupting one of said circuits to intermittently operate said signal, a battery for operating said second means, another battery, said last means also for including said batteries in series with said line to enable said line to disconnect said first means.

7. In a telephone system, a line, a signal for said line, a pair of circuits, means for operating said signal, said means associated with said circuits, means for connecting said operating-means and said signal over one of said circuits to operate said signal thereover, and for connecting said means and said signal over the other of said circuits to operate said signal over said other circuit, and means for inten'uptingsaid other circuit to intermittently operate said signal, a battery for operating said second means, an other battery, said last means also for including said batteries in series with said line to enable said line to disconnect said first meansL i 8. In a telephone system, a line, a signal for said line, a source of current for operating said signal, a circuit comprising two branches for connecting said source over said line to said signal, means for closing one of said branches to operate said signal and for opening said last branch and closingthe other of said branches to control the operation of said signal, means for interruptingsaid other branch to intermittently operate said signal, a battery for operating said first means, another battery, said last means also for including said batteries in a circuit with said line to enable said line to disconnect said source of current;

9. In a telephone system, a calling line, a called line, a signal for the called line, a source of current for operating said signal, progressively movable switching, mechanism for establishing a connection from said calling line to said called line, a pair of circuits, means for connecting said source. and said signal over one of said circuits to operate vals, a battery for operating said first means, another battery, said last means also for including said batteriesv in a circuit with said line to enable said line to disconnect said source of current.

10. In a telephone system, a calling and a called line, progresslvely movable automatic switches for establishing a conne tion between said lines, a signal for the called line, a source of current for operating said signal, a circuit comprising two branches for connecting said source to said signal after said connection is established, means for closing one otsaid branches to operate said signal and'for thereafter opening said last mentioned branch and closing the other branch to operate said signal, and means for interrupting said other branch to intermittently operate said signal, a battery for operating said first means, another battery, said last means also'for including said batteries in a circuit with said line to enable said line to disconnect said source of current.

11. In a telephone system, a calling line,

a called'line, a plurality of progressivelysignal for the called line, a source of cur;

rent for operating said signal, a circuit individual to one of said switches, a circuit ing said source over said common circuit to said signal to operate the same, and means for interrupting said common circuit to intermittently operate said signal, a battery for operating said first means, another battery, said last means also for including said batteries in a circuit with said line to enable said line to disconnect said source of current. a

12. In a telephone system, a calling line a called line, a plurality of progressively movable switches, means whereby the call ing line finds one of said switches to extend a'connection to said called line, a signal for said called line, a source of current for operating said signal, a circuit individual to one of said switches, a circuit common to said plurality of switches, means for connecting said source and said signal over said individual circuit to operate said signal and forthen connecting said source and said signal over said common circuit to operate said signal over said common circuit, and means for intermittently interrupting said common circuit to intermittently operate said signal, a battery for operating said second means, another battery, said last means also for including said batteries in a circuit with said line to enable said line to disconnect said source of current. a

13. In a telephone system, a first line, a callingline, a signal for said first line, a source of current for operating said signal, a battery for operating purposes, a relay for disconnecting said source, means for connecting said calling line and said first line and for including said relay and battery in circuit during signaling whereby when the first line answers if the said first line is short the relay will energize to cut ofl said source of current but it the line is long the relay "fails to operate, another battery, and means for thereafter including said batteries in the circuit of said relay to enable said first line to operate said relay todisconnect 5 said source of current if the said first line is long.

14. In a telephonesystem, a calling'line, a called line, a plurality of progressively movable switches, any one of which will serve the purpose of the calling line for establishing a connection to said called line, a signal for the called line, a source of current for operating said signal, a circuit individualto one of said switches, a circuit common to said switches, a slow magnet for connecting sald source over said indlvldual circuit to operate said signal and for then connecting said source over said common circuit to said signal to operate the same, and a magnet for interrupting said'co'rnmon circuit to intermittently operate said signal.

15. In a telephone system, a calling line, a called line, a plurality of sets of progressively movable switches, any set of which will serve the purpose of the calling line for extending a connection to the called line, a signal for the called line, a source of current for operating said signal, a circuit common to said switches for connecting the said source with said signal when said connection is established, a magnet for interrupting said circuit to intermittently operate said signal, and a slow magnet including a circuit individual to one of said switches and independent of said interrupting magnet for connecting said source with said signal to operate the same.

16. In a telephone system, a calling line, a called line, a plurality 'of'progressively movable switches, means whereby the calling line finds'one. of said switches to extend a connection to said called line, a signal for said called line, a source of current for operating said signal, a circuit individual to one of said switches, a circuit commonv to 'saidplurality of switches, a magnet for connecting said source and said signal over said individual circuit to operate said signal and for then connecting said source and said signal over said common circuit to operate said signal over said common circuit.

- '17. In a telephone system, a calling line, a called line, a plurality of progressively movable switches, means whereby the calling line finds one of said switches to extend a connection to said called line, a signal "for said called line, a source of current for operating said signal, a circuit individual to one of said switches, a circuit common to said plurality of switches, a slow magnet for connecting said source and said signal a over said individual circuit to operate said signal for then connecting said source and said signal'over said common circuit to operate said signal over said common circuit.

18. In a telephone system, a calling line, a called line, a plurality of progressively movable switches, meanswhereby the calling line finds one of said switches to extend a connection to said called line, a signal for said called line, a source of current for operating said signal, a circuit individual to one of said switches, a circuit common to said plurality of switches, a relay for connecting said source and said signal over said indi,-

vidual circuit to operate aid signal and for 7 ing said source of current and said signal, a slow magnet for controlling the operation of said signal over one of said circuits and then the other, a magnet for interrupting one of said circuits to intermittently operate said signal, a battery for operating said second magnet, another battery, said second magnet also for including said batteries in series with said line to enable said line to discon nect 'said source of current.

20. In a telephone system, a line, a signal for said line, a source of current for operating said signal, a circuit comprising two branches for connecting said source over said line to said signal, a slow relay for closing one of said branches to operate said signal and for opening said last branch and closing the other of said branches to control the operation of said signal, a relay for interrupting said other branch to intermittently operate said signal, a battery for operating said slow relay, another battery, said second relay also for including said batteries in a circuit with said line to enable said line to disconnect said source of current.

21. In a telephone system, a calling line, a called line, a signal for the called line, a source of current for operating said signal, progressively movable switching mechanism for establishing a connection from said calling line to said called line, a pair of circuits, a magnet for connecting said source and said signal over one of said circuits to operate said signal when connection is completed to said called line and for then connecting said source and said signal over the other of said circuits to operate said signal over the other circuit, and another magnet for interrupting said other circuit to operate said signal at intervals, a battery for operating said magnet, another battery, said other magnet also for including said batteries in a circuit with said line to enable said line to disconnect said source of current.

22. In a telephone system, a calling line, a called line, a signal for the called line, a source of current for operating said signal, progressively movable switching mechanism for establishing a connection from said calling line to said called line, a pair of circuits, a slow relay for connecting said source and said signal over one of said circuits to operate said signal when connection is completed to said called line and for then connecting said source and said signal over the other of said circuits to operate said signal over the other circuit, and a relay for interrupting said other circuit to operate said signal at intervals, a battery for operating said first slow relay, another battery, said second relay for including said batteries in a circuit with said line to enable said line to disconnect said source of current.

Signed by me at Chicago, Cook county, Illinois, this 21 day of April, 1916.

TALBOT G. MARTIN.